The present invention relates generally to the field of fuel cells, and more specifically to fuel cells comprising liquid electrolytes.
Various types of fuel cells are known in the art as devices that convert energy from a chemical reaction into electrical energy. Each type of fuel cell has one or more limitations that currently restrict its use to specialized applications. For example, thermally regenerative liquid fuel cells induce hydrogen flow by thermal decomposition of a mixture of lithium hydride and sodium hydride, at a high temperature (for example from about 800° C. to about 1300° C.) maintained by a separate heating device to generate hydrogen. The hydrogen is then passed through the cell at a high pressure (10 atmosphere or above) to mobilize hydride ions, which release electrons at the electrodes for generating electricity. Only a small portion of thermal energy is converted to electrical energy. The requirements of a high temperature heating device and capability of handling high pressure gas increases design complexity including limitations in size and cost. Another example is conventional hydrogen-oxygen fuel cells, where the electrolytes used have a limited mobility for mass transport of positive hydrogen ions (H+) and therefore the generated electrical energy is much less as compared to that ideally available from the electrochemical conversion. Furthermore, in other types of fuel cells such as those using polymer electrolytes, there is a considerable risk of poisoning of electrodes due to the presence of gaseous impurities such as carbon monoxide, hydrogen sulfide, chlorine etc.
Solid oxide fuel cells use metal oxide ceramic electrolytes in solid state. These electrolytes operate at a temperature as high as about 1000° C. This high operating temperature allows transport of oxygen ions, which release electrons at the electrode for generating electricity. However, the use of fragile ceramic electrolytes, the requirement of structural materials sustainable at high temperature, and the requirement of additional cooling systems limit the reliability of solid oxide fuel cells.
Therefore, there is a need in the art for fuel cells that efficiently and reliably operate at lower temperatures than current fuel cells.